Natural wood, with its unique grain patterns, is what gives traditional
acoustic instruments warm and distinctive sounds, while the power of
modern electronic processing provides an unlimited degree of control to
manipulate the characteristics of an instrument's sound. Now, a guitar
built by a student at MIT's Media Lab promises to provide the best of
both worlds.

The Chameleon Guitar — so named for its ability to
mimic different instruments — is an electric guitar whose body has a
separate central section that is removable. This inserted section, the
soundboard, can be switched with one made of a different kind of wood,
or with a different structural support system, or with one made of a
different material altogether. Then, the sound generated by the
electronic pickups on that board can be manipulated by a computer to
produce the effect of a different size or shape of the resonating
chamber.

Its creator, Media Lab master's student Amit Zoran,
explains that each piece of wood is unique and will behave in a
different way when it is part of an instrument and begins to vibrate in
response to the strings attached to it. Computers can't model all the
details of that unique responsiveness, he says. So, as he began
experimenting with the design of this new instrument, he wondered "what
would happen if you could plug in acoustic information, like we do with
digital information on a memory stick?"

Under the direction of Media Lab Associate Professor Pattie Maes, and
with help from experienced instrument builder Marco Coppiardi, he built
the first proof of concept version last summer, with a variety of
removable wooden inserts. The concept worked, so he went on to build a
more polished version with an easier quick-change mechanism for
switching the inserts, so that a musician could easily change the sound
of the instrument during the course of a concert — providing a variety
of sound characteristics, but always leaving the same body, neck and
frets so that the instrument always feels the same.

With
Coppiardi's help, he selected spruce and cedar for the initial
soundboard inserts. This January, he demonstrated the new instrument at
the annual Consumer Electronics Show in Las Vegas, where it received an
enthusiastic response. He also demonstrated the earlier version at two
electronics conferences last year.

The five electronic pickups
on the soundboard provide detailed information about the wood's acoustic
response to the vibration of the strings. This information is then
processed by the computer to simulate different shapes and sizes of the
resonating chamber. "The original signal is not synthetic, it's
acoustic," Zoran says. "Then we can simulate different shapes, or a
bigger instrument." The guitar can even be made to simulate shapes that
would be impossible to build physically. "We can make a guitar the size
of a mountain," he says. Or the size of a mouse.

Because the
actual soundboard is small and inexpensive, compared to the larger size
and intricate craftsmanship required to build a whole acoustic
instrument, it will allow for a lot of freedom to experiment, he says.
"It's small, it's cheap, you can take risks," he says. For example, he
has a piece of spruce from an old bridge in Vermont, more than 150 years
old, that he plans to use to make another soundboard. The wooden beam
is too narrow to use to make a whole guitar, but big enough to try out
for the Chameleon Guitar.

The individual characteristics of a
given piece of wood — what Zoran refers to as the "romantic value" of
the material, "is very important for the player," he says, and helps to
give an individual instrument a particular, unique sound. Digital
processing provides an infinite range of variety. "Now," he says, "it's
possible to have the advantages of both."

For now, Zoran is
concentrating on developing the guitar as a thesis project for his
master's degree, and hopes to continue working on it as his doctoral
thesis project. After that, he says, he hopes it will develop into a
commercial product.